Date: Fri, 5 Jul 2013 12:14:09 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Daniel Kalchev" <daniel@digsys.bg>, <freebsd-fs@freebsd.org> Subject: Re: Slow resilvering with mirrored ZIL Message-ID: <13061C613C1B4FE597DA5984CAFBA14C@multiplay.co.uk> References: <CABBFC07-68C2-4F43-9AFC-920D8C34282E@unixconn.com><51D42107.1050107@digsys.bg><2EF46A8C-6908-4160-BF99-EC610B3EA771@alumni.chalmers.se><51D437E2.4060101@digsys.bg><E5CCC8F551CA4627A3C7376AD63A83CC@multiplay.co.uk><CBCA1716-A3EC-4E3B-AE0A-3C8028F6AACF@alumni.chalmers.se><20130704000405.GA75529@icarus.home.lan><C8C696C0-2963-4868-8BB8-6987B47C3460@alumni.chalmers.se><20130704171637.GA94539@icarus.home.lan><2A261BEA-4452-4F6A-8EFB-90A54D79CBB9@alumni.chalmers.se><20130704191203.GA95642@icarus.home.lan><43015E9015084CA6BAC6978F39D22E8B@multiplay.co.uk> <CAOjFWZ4obK1cSmvTpW%2Bt4xKdMf%2BkJV5w-sujDT1AZoepj%2B5YrA@mail.gmail.com> <3CFB4564D8EB4A6A9BCE2AFCC5B6E400@multiplay.co.uk> <51D6A206.2020303@digsys.bg>
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----- Original Message -----
From: "Daniel Kalchev" <daniel@digsys.bg>
To: <freebsd-fs@freebsd.org>
Sent: Friday, July 05, 2013 11:37 AM
Subject: Re: Slow resilvering with mirrored ZIL
>
> On 05.07.13 02:28, Steven Hartland wrote:
>>
>>
>> If anyone wants my current patches which add switch to 4k ashift by
>> default
>> as a sysctl + works with QUIRKS too, just let me know.
>>
>> They are well tested, just we want more options before putting in the
>> tree.
>
> Is it not easier to add this as an option to zpool create, instead of an
> sysctl?
That wouldn't achieve what I wanted which was to clamp all pools created
to a min of XYZ, instead of having to remember to always add the 4K option
to every pool command.
This doesn't remove the requirement for an option to zpool create, zpool
add etc, which is what I still need to implement.
> That is, I believe we have two scenarios here:
>
> 1. Having an sysctl that instructs ZFS to look at the FreeBSD quirks to
> decide what the ashift should be, instead of only querying the
> 'sectorsize' property of the storage. I believe we might not even need
> an sysctl here, just make it default to obey the quirks --- but sysctl
> for the interim period will not hurt (with the proper default).
While most people will want this behaviour some may not so I currently have:
vfs.zfs.min_create_ashift: Minimum ashift used when creating new pools
vfs.zfs.vdev.optimal_ashift: Enable/disable optimal ashift usage on initialisation
> 2. Have an option to zpool create and zpool add, that specifies the
> ashift value. Here my thinking is that it should let you specify an
> ashift equal or larger than the computed one, which is based on the
> largest sector size of all devices in a vdev.
Exactly whats planned.
> Don't know, but always wondered.. how hard is it to change the ashift
> value on the fly? Does it impact reads of data already on the vdev, or
> does it impact only writes? If only writes, it should be trivial, really....
I've not looked in depth but considering even adding an device with
a larger ashift requirement is prevented I'd say this is going to
be none trivial.
Regards
Steve
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